1. Field of the Invention
The present invention relates to a projection type display configured to project an image onto a projection surface.
2. Description of the Related Art
Conventionally, a projector configured to provide autofocus (“AF”) utilizing a phase difference detection method is known. See, for example, Japanese Patent No. 3,120,526 and Japanese Patent Laid-Open No. 2004-102009. A projector configured to provide the AF utilizing a mountain climbing method is also known. The mountain climbing method is an approach to measure the contrast of a projected image by slightly moving a focus position, and to determine a contrast peak position to be an in-focus position to be focused in the AF. Characteristically, the mountain climbing method can more stably and precisely calculate the in-focus position than the phase difference detection method. However, the mountain climbing method repeats lens driving and a contrast measurement process many times, and thus requires a longer time to complete the AF than the phase difference detection method.
In order to improve the focusing precision and to shorten the process time period of the AF, a hybrid method is proposed which quickly moves a focus lens near to an in-focus position by the phase difference detection method, and then moves the focus lens to the in-focus position by the mountain climbing method so as to improve the focusing precision. See, for example, Japanese Patent Laid-Open No. 2004-93890.
However, the hybrid method that combines the phase difference detection method and the mountain climbing method still needs a longer time to complete the AF due to a combination with the mountain climbing method, and thus it is preferred to avoid the combination with the mountain climbing method as long as the focusing precision is secured. Nevertheless, when a projected image significantly blurs because the focus lens is distant from the in-focus position, the in-focus position cannot be precisely calculated by utilizing only the phase difference detection method.